Re-powering 3.0L -> 4.3L? Is it difficult?

gtochris

Senior Chief Petty Officer
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Aug 4, 2010
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742
Cold winter thought:

Since my engine is 17 years old (runs good), if it suddenly went, how much effort would it be to upgrade to a 4.3L (assuming the 190hp carb version) since I'm thinking the MPI would be too much $$ and add to complexity for a basic boat?

My model offered both engines so I'm assuming it would bolt right in? Any complexity to wiring? Would I be best served getting an engine built before a certain year for easier connection?

Thanks.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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50,758
Re: Re-powering 3.0L -> 4.3L? Is it difficult?

pull everything from carb to prop and replace with everything from carb to prop. glass in new mounts.

I would first find out why your existing motor "suddenly went"
 

Howard Sterndrive

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Nov 5, 2008
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4,603
Re: Re-powering 3.0L -> 4.3L? Is it difficult?

it's a lot of work. I did mine a few years ago. New drive ratio required as well as making the motor mounts.

How big is your fuel tank? If it's less than 23gal. don't do it.
My boat has a 30 gal tank otherwise I would have stayed with the 3.0

Everything from the flywheel back was compatible on mine - I used the same flywheel cover, and all transom parts.

I went from a top speed of 35mph to 49mph though.
 
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americanmcss

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Jul 18, 2012
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Re: Re-powering 3.0L -> 4.3L? Is it difficult?

Depending on how large and what kind of boat you have, upgrading from a 3.0 to 4.3 wouldn't be too difficult minus what Bubba and Scott have already discussed. I know that for a lot of I/O the engine compartment was the same size from 4cyl to even v8 models circa the last two decades, so space wouldn't be much of an issue.

Last winter we did a complete overhaul on our boat from carb to prop (started with and kept our 5.0L HO however), and even gave the trailer a good once over. It was extremely frustrating at times especially when it came to recon-ing the outdrive. Expect to strip the I/O system down to nothing if you do go after this project because it will require you to do so.

If your boat's 3.0 gives up for whatever reason, and its more power you are after, I would highly recommend purchasing a new boat altogether, that has the motor/outdrive package you want already installed. Depending on how your motor dies, (which typically results in lack of proper maintenance and rarely due to normal wear, not pointing fingers just stating what i've read and experienced), it could be reconditioned and sold to help pay for your new boat.

Two other factors you will want to take into consideration is your attachment to the boat, whether its emotional, financial or otherwise, and your skills as a mechanic. We had three guys working on our boat with close to 50 years of combined professional mechanical, woodworking, and fabricating experience, albeit none of it marine, and it was still a headache. An OEM service manual for every facet of the job is a must have!

Good luck to you sir if this is indeed a project you take on!
 

gtochris

Senior Chief Petty Officer
Joined
Aug 4, 2010
Messages
742
Re: Re-powering 3.0L -> 4.3L? Is it difficult?

it's a lot of work. I did mine a few years ago. New drive ratio required as well as making the motor mounts.

How big is your fuel tank? If it's less than 23gal. don't do it.
My boat has a 30 gal tank otherwise I would have stayed with the 3.0

Everything from the flywheel back was compatible on mine - I used the same flywheel cover, and all transom parts.

I went from a top speed of 35mph to 49mph though.

What boat did you do this on?

I think the 4cyl and V6 shared the same outdrive gear ratio? , my model (190 RS) had an optional 4.3L so I'm assuming because of that the engine mounts would be the same?

My engine runs strong, I think it is seeping a bit of oil around the gasket but really minimal- I've given it a full tuneup every other year I've had it thus far. I guess if put in that position another 3.0L is the answer:)
 
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matt167

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Sep 27, 2012
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4,199
Re: Re-powering 3.0L -> 4.3L? Is it difficult?

3.0L is a 1.98:1 ratio. 4.3L will be 1.84:1.

The stringer mounts for the engine is placed differently, but who knows. you may have the other stringer setup there and waiting
 

thumpar

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Jun 21, 2007
Messages
6,138
Re: Re-powering 3.0L -> 4.3L? Is it difficult?

If it was me I would just sell the boat and buy a boat with the power you want. It would probably be cheaper and wouldn't require all the work.
 

Howard Sterndrive

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Nov 5, 2008
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Re: Re-powering 3.0L -> 4.3L? Is it difficult?

What boat did you do this on?
92 Bayliner 1851CB
cheaptrick007.jpg

still says 3.0 below the "Capri" to this day.meant to peel the decals off.
cheaptrick002.jpg


drive ratio is not the same. you also need to buy a Y pipe for the exhaust. I bought a complete 2008 Merc manifold and Y pipe set up new from ebay cheap so I have dry joint manifolds which are sweet..

Does your 3.0 have power steering? You'll probably want to consider that on a 4.3
There was a 4.3 version of my boat model offered in 92, but my hull was only set up for a 3.0 -was not built with side mount pads - had to build them.
Bayliner didn't put anything in that wasn't exactly what was called for on that unit.

This is actually my 2nd swap from 3.0 to V6 - I also converted my Grew 175. It has a 17 gal tank. I can empty it in an hour :(
That's why I made sure this boat had a big gas tank before beginning.
 
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gtochris

Senior Chief Petty Officer
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Aug 4, 2010
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Re: Re-powering 3.0L -> 4.3L? Is it difficult?

[QUOTE
Does your 3.0 have power steering? You'll probably want to consider that on a 4.3
There was a 4.3 version of my boat model offered in 92, but my hull was only set up for a 3.0 -was not built with side mount pads - had to build them.
Bayliner didn't put anything in that wasn't exactly what was called for on that unit.

This is actually my 2nd swap from 3.0 to V6 - I also converted my Grew 175. It has a 17 gal tank. I can empty it in an hour :(
That's why I made sure this boat had a big gas tank before beginning.[/QUOTE]

Nice boat!
I do have the power steering. I did some looking as I believe my tank is 23 gallons where as the version of my boat with the V6 I believe holds 27-30 however we are on a somewhat normal size lake so range isnt a question for me.

Thanks for all the tips. I didnt realize this swap would be so complex.
 
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